textproduct: Albany

WHAT HAS CHANGED

Winter weather advisories issued for most of the region, except the Mid Hudson Valley, from Thursday evening through noon Friday for a wintry mix, including freezing rain. Temperatures have continued to trend colder for this event. Also trended temperatures down Saturday, which should reduce the amount of snow melt and limit hydro concerns through this weekend.

KEY MESSAGES

1) Patchy black ice will be possible tonight, which could result in slippery travel conditions.

2) Rain changing to a wintry mix will result in more widespread slippery travel conditions Thursday night into Friday, including for the Friday AM commute.

3) High confidence in above normals temps late in the weekend into early next week. Combined with continued chances for rainfall, this will result in snowmelt and increased runoff. The potential for ice jams and flooding looks to increase during this time with perhaps isolated issues.

DISCUSSION

KEY MESSAGE 1... As of 1:55 PM EST...Current sfc analysis shows a narrow ridge of high pressure moving over the region. With large-scale subsidence in place, skies have become mostly clear as low stratus from earlier this morning has mixed out. The 12z KALY sounding showed a very strong low-level inversion, with very dry air above this. Given the AM clouds and the strength of the inversion, many valley areas are having trouble warming out of the low to mid 40s, but some of the high terrain areas of the Catskills and southern Taconics that are above the inversion are seeing temps in the low 50s. As cloud cover continues to diminish through the afternoon, expecting temperatures region- wide to rise a few to several more degrees. However, clear skies and calm winds initially tonight will allow temperatures region-wide to fall back near or below freezing. This may allow for patchy black ice to form tonight from any snow that melts this afternoon. Will also mention potential for fog tonight given favorable radiational cooling conditions and availability of low-level moisture from melting snow. Will handle this with SPSs as necessary tonight.

KEY MESSAGE 2... Tonight into tomorrow morning, a broad 1040+ mb sfc high will build into Quebec beneath confluent flow aloft as a potent upper shortwave and associated sfc low track towards our region from the Ohio Valley. As mid-level isentropic lift ahead of the system's warm front increases tomorrow, we should precipitation spread from south to north across the region through the day. Precipitation will initially be mostly rain.

However, there is a strong signal for low-level cold air damming and northerly ageostrophic flow beneath the right entrance region of the upper jet to develop Thursday evening and night. So, the mid-level warm front will lift across the region, but the sfc warm front remains to our south. Strengthening LLJ will aid in moisture transport into the region by Thursday evening, and will also allow for stronger isentropic lift and a band of mid-level FGEN developing. When combined with increasing CVA as the upper shortwave approaches from the west, precip rates and coverage should increase as temperatures begin to fall. Therefore, we are expecting a transition to a wintry mix, including sleet and freezing rain, for much of the region outside of the Mid Hudson Valley. Temperatures have trended colder with this system per today's 12z guidance, but still low confidence on how much precip falls as sleet vs freezing rain. The HRRR even brings in enough low-level cold air to change precip over to snow north of I-90 Friday morning, but seems to be an outlier with this solution so we tended to keep more of a wintry mix in the forecast.

By the time precip tapers off late Friday morning, up to an inch or so of snow/sleet accumulation is expected, mainly for northern areas. The bigger concern will be the freezing rain, with a glaze to a tenth of an inch for the Capital District, Mohawk Valley, and CT River Valley. The greatest ice amounts of a tenth to around a quarter of an inch are expected across the southern ADKs and high terrain of western New England. Based on the colder forecast trend and potential impacts to the Friday AM commute, there was good agreement with neighboring WFOs to issue winter weather advisories from Thursday evening through noon Friday. Have been fairly aggressive with the coverage of the advisory given the colder shift in guidance, but still can't rule out additional portions of the Mid Hudson Valley needing to be added if the forecast continue to trend cooler. Will also note that the main concern with these ice amounts is for slippery travel conditions, as ice amounts generally don't look high enough to result in significant power outage concerns.

KEY MESSAGE 3... We dry out Friday afternoon and night, with a significant pattern change expected. A sub 990 mb sfc low will track through the Great Lakes Friday night into Saturday. Out ahead of this low, 850 mb temps increase to +12 to +14C across our area as the southwesterly LLJ strengthens to around 50 kt. These 850 mb temps are +2-3 sigma per the NAEFS. However, at the surface, forecast soundings are showing a wedge of low-level cool air that may be tough to scour out, at least through much of the day. We still have forecast highs in the 50s for western areas, but for much of western New England, we collaborated with GYX and BOX to lower temps a few to several degrees from the NBM, with highs mainly in the 40s. NBM continues to be quite warm relative to other guidance Saturday, so future downward adjustments to temperatures may still be needed. Saturday evening or night, the system's cold front tracks through the region with scattered showers and perhaps even a rumble of thunder for western areas. We then dry out an cool down slightly for Sunday.

Given that the upcoming weather system has trended cooler with more frozen vs liquid precip, combined with the fact that Saturday temperatures look cooler/the warm up may be shorter lived than preciously expected, the potential for hydro issues appears lower than previously expected. For most rivers, creeks, and streams, the NERFC is not expecting enough of a rise to result in significant ice break up. However, will continue to mention that isolated issues can't be ruled out, mainly south of the Capital District where less precip will be frozen Thursday night into Friday.

For the first half of next week, upper ridging over the east coast amplifies once again as another area of low pressure tracks to our west. This will result in continued warm advection Monday through Wednesday of next week. There is high confidence in above normal temperatures, but still some question as to just how warm we get. There is a very strong signal for anomalous warmth from the 00z ECMWF ensemble, which showed an EFI of 0.8 to 0.9, and a SoT >0, which is impressive to see this far out. However, some of today's 12z guidance has trended slightly cooler. Nevertheless, the current forecast is for temperatures Tuesday and Wednesday well into the 60s for many valley areas. Given that rivers will already be elevated at this time from prior qpf and snow melt, more substantial river rises are possible if the current temperature forecast holds. Current NAEFS and HEFS guidance shows a low (10-30%) chance for some area rivers and stream to hit minor flood stage. These river rises would also be enough to result in more widespread breakup of ice, so some additional ice jam issues could be possible as well. Fortunately, most of the guidance that shows a significant warm up also keeps us fairly dry through mid-week. Will continue to closely monitor over the coming days.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

Through 18z Thursday...Main forecast challenge is when low level stratus clouds finally scour out this afternoon. Satellite trends have shown progress with clearing occurring, especially at KALB/KPSF/KGFL, with thicker cloud cover at KPOU. Some initial fluctuation of VFR/MVFR cigs will likely occur at KALB/KGFL for an hour or two, although it may take 3-4 hours for the clouds to dissipate later this afternoon at KPOU. Once clearing occurs, that will actually set the stage for widespread low clouds and fog to develop tonight due to high pressure overhead and residual low level moisture. Will mention MVFR/IFR conditions developing shortly after 00z, then LIFR/VLIFR by 05z-06z. Visibility should marginally improve by around 14z-15z Thursday, but could still be IFR/MVFR levels while cigs expected to remain IFR through 18z as a front approaches from the south. Most sites will remain dry through 18z, however -RA is expected to develop at KPOU by around 12z. Winds will be variable around 3-6 kt through the day, becoming near calm tonight.

Outlook...

Thursday Night: High Operational Impact. Definite RA...SN...FZRA...SLEET. Friday: Moderate Operational Impact. Chance of RA...FZRA. Friday Night: Low Operational Impact. Slight Chance of SHRA. Saturday: Low Operational Impact. NO SIG WX. Saturday Night: High Operational Impact. Likely SHRA. Sunday: No Operational Impact. NO SIG WX. Sunday Night: No Operational Impact. NO SIG WX. Monday: No Operational Impact. NO SIG WX.

ALY WATCHES/WARNINGS/ADVISORIES

CT...Winter Weather Advisory from 5 PM Thursday to noon EST Friday for CTZ001-013. NY...Winter Weather Advisory from 5 PM Thursday to noon EST Friday for NYZ032-033-038>043-047>054-058-061-063-082>084. MA...Winter Weather Advisory from 5 PM Thursday to noon EST Friday for MAZ001-025. VT...Winter Weather Advisory from 5 PM Thursday to noon EST Friday for VTZ013>015.